Cathode ray tube counting device



Sept. 8, 1959 w. F.'SCHREIBER 2,903,616

CATHODE RAY'TUBE COUNTING DEVICE Original Filed Feb. 28. 1955 l l2 no lli F|G.2bv 7 MASK AMPL.

VOLTAGE CHARACTERISTIC VOLTAGE DOWN O 7 up BEAM DEFLECTION 2 TRIGGE R m cmcun PHOTOGELL F I 4 PHOTOCELL AMPLIFIER TRIGGER CIRCUIT SHIFT PULSE? 'INVENTOR WILLIAM F. SCHREIBER ATTORNEY United Statesv Patent Patented Sept. 8, 1959 2,903,616 CATHODE RAY TUBE COUNTING DEVICE William F. Schreib'er, North Hollywood, Calif., assignor,

by mesne assignments, to 'Sylvania Electric Products Inc., Wilmington, Del., a corporation of Delaware Original application February 28, 1955, Serial No. 490,750, new Patent No. 2,870,369, dated January 20, 1959. Divided andthisapplication October 24, 1958,

Serial No. 775,669

4 Claims. (Cl. 315-10) My invention relates to electronic switching apparatus and more particularly relates to cathode ray tube circuits for use'in such apparatus. This application is a division of application Serial No. 490,750 filed February 28, 1955.

The prior art has knowledge of circuits of this type in which the cathode ray tube is provided with a plurality of anodes, the electron beam produced within the tube being directed sequentially upon each anode individually in accordance with externally supplied electric pulses. -Such tubes require complicated and expensive electrode structures; further, it is a tedious, time consuming, and diflicult procedure to mount these electrodes in proper manner within the tube envelope.

I have invented a cathode ray tube circuit of the character indicated in which these difliculties are obviated.

Accordingly, it is an object of the present invention to provide a new and improved cathode ray tube circuit of the character indicated.

Another object is to provide a new and improved cathoderay tube circuit of the characterindicated which makes use of a conventional cathode ray tube and a novel externally mounted optical mask or wedge.

Still another object is to provide a new and improved cathode ray tube circuit adapted for use in switching apparatus'and including, in operative relationship, a conventional cathode ray tube, an externally mounted optical wedge or mask, a photocell and a feedback amplifier.

Yet another object is to provide a new and improved cathode ray tube circuit of the character indicated which incorporates a novel optical mask or wedge and which obtains a switching action with the use of one or two dimensional scanning.

These and other objects of the invention will either be explained or will become apparent to those skilled in the art when this specification is studied in conjunction with the accompanying drawings wherein:

Fig. 1 illustrates an embodiment of the basic invention as applied to one dimensional scanning; v

Fig. 2 and 2 b illustrates alternate types of optical Wedges and masks foruse in the apparatus of Fig. 1;

Fig. 3 is a diagram illustrating graphically the voltage deflection characteristic of the invention of Fig. 1;

Fig. 4 illustrates a second-embodiment of the basic invention as applied to two dimensional scanning; and

Fig. 5 illustrates an optical wedge or mask for use with the apparatus of Fig. 4.

In accordance with one main feature of the invention, I provide a conventional cathode ray tube provided with means for producing 'an electron beam, a luminescent screen upon which the beam is directed, and a pair of deflector plates for deflecting the beam in one given dimension, for example, horizontally or vertically. An optical mask provided with a plurality of like sections spaced sequentially along the given direction is positioned in front of the luminescent screen. Each section is transparent and the transparency varies from point to point within each section in the same manner. As the beam passes over each section, the passage "can be observed visually. A photocell is mounted 'in front of the mask and responds to the luminescent information appearing in the mask to develop a voltage proportional thereto. As the beam position within any mask section is varied along the given direction, the photocell output voltage will be varied accordingly because of the transparency variations within the section. This varying output voltage is amplified, if necessary, and then is supplied as a feedback voltage to the deflection plates. The purpose of this feedback voltage is to stabilize the beam position within any section; if voltage supply variations or the like result in beam movement within the section, the feedback voltage will act to restore the beam to its stable position within the section. A beam shifting signal, for example, in the form of discretely spaced pulses is also supplied to the deflector plates; 'this signal is sufliciently large to momentarily override the feedback voltage and thus shift the beam from one section to the adjacent section. Means are further provided to return the beam to its original position after the beam has been shifted through all other positions successively. In this fashion the beam attains different stable positions in accordance with the number of incomingpulses, so that my apparatus can be used, for example, as a counter or sealer.

In order to increase the number of stable beam positions beyond that available with one dimensional beam travel or scanning, and thus, for example, increase the capacity of the counter or sealer, it is necessary to use two dimensional beam deflection; this can be accomplished through the use of horizontal and vertical deflection plates, normally provided within the cathode ray tube. To this end, another type of optical mask is required. This mask "is divided into a plurality of like horizontal segments, each segment having a plurality of like sections. Each section has a light transmission characteristic such that variations of beam position. in

the horizontal direction within the section produce light variations in one band of wavelengths, while beamvariations in the vertical direction produce light variations the other frequency range supplies a second feedback voltage to the vertical deflection plates to maintain vertical beam stability. The system otherwise responds in the same manneras before except that means are required not only to return the beam horizontally after a complete horizontal segment of the mask has been scanned but also to move the beam vertically at the same time so that the adjacent horizontal segment can also be scanned.

Referring now to Fig. 1, there is provided a conventional cathode ray tube with an electron gun and beam focusing structure identified in block format 101,, vertical deflection plates 102a and 102b, and a luminescent screen 103. Secured to the outside of screen is an optical mask 104. A photocell 105 is mounted adjacent screen 103. The output voltage produced by photocell 105 is supplied to the input 106 of amplifier 107. The output of amplifier 107 is connected through resistor 108 to deflection plate 102a, to the input 110 of trigger circuit 111 and to output terminal 112. Incoming discretely spaced pulses with the wave form indicated are supplied to input terminal 113. This terminal is connected through resistor 114 to plate 102a. The output 115 of trigger circuit 111 is connected to input 1160f amplifier 107.

Fig. 2a shows one form of optical mask 104 whichcan be used with the apparatus of Fig. 1. It includes a plurality of sections, in this example five sections, identified as 104a, 104b, 104e, 104d and 104e. Each section includes an optically transparent portion and a shaded portion which is appreciably more opaque, the opacity increasing .toward the top of each portion. The mask is mounted adjacent screen 103 in such a manner that the longdimension of the screen extends along the beam deflection path.

Fig. 3 is a composite graph showing a sawtooth pattern which indicates the variation in the output voltage of amplifier 107 with electron beam deflection for the five section mask of Fig. 2a. Superimposed upon this pattern is a line which indicates the tube deflection characteristic (i.e., beam deflection vs. deflection voltage). The circled intersections of line and sawtooth represent stable positions of the electron beam. (The uncircled intersections are unstable because a slight random displacement in either direction results in positive feedback; this positive feedback forces the beam to move away from any unstable position.) The circled positions are stable because any voltage fluctuation at the plate will shift the beam position, and as a result of the optic-a1 properties of the mask, will change the voltage output of the photocell. The voltage output from the amplifier will change accordingly. This change in amplifier voltage will be applied to the deflection plates in such manner that the beam 'will be restored to its original stable position.

As can be seen from Fig. 3, there is a characteristically different amplifier output for each stable beam position. When the beam attains an extreme horizontal position, this amplifier voltage attains such a value that the trigger circuit is activated and produces a shift pulse which after amplification is supplied to the deflection plate to return the beam to its initial horizontal position.

In the absence of a shift pulse, the amplifier output voltage appearing at output terminal 112 is proportional .to the horizontal beam position, and hence the apparatus of Fig. 1 can be used as a counter.

Fig. 2b shows an alternate type of optical mask 117 wherein each section has a wedge shaped opaque portion. This mask can be used in place of the mask of Fig. 2a if the electron beam is focused to produce a fairly large luminescent spot on the screen so that varying portions of the spot are concealed behind the opaque portion.

For combined horizontal and vertical scanning, the apparatus of Fig. 1 must be modified as shown in Fig. 4,

and a dilferent mask, for example as shown in Fig. 5, must be used.

The mask 200 of Fig. 5 comprises a plurality of like small clear transparent areas 201a, 201b, 201c, 201d, 201e, 201 201g, 20111, and 201i. Each of these areas represents a stable beam position. It will be seen that there are three horizontal groups or arrays, each containing three of the above areas. The number of arrays and included areas can be indefinitely extended to cover virtually the entire surface of the associated cathode ray tube screen.

The mask portions 202 horizontally adjacent to each area and identified by one type of characteristic shading are red colored and transparent. The mask portions 203 vertically adjacent to each area and identified by another type of characteristic shading are blue colored and transparent. Each of these portions acts as a light filter for any luminescent spot appearing in the tube screen and has a different frequency transmission characteristic.

The mask 200, which in this case contains one hundred areas in a square ten areas in a side, is mounted adjacent the screen 101 of tube cathode ray tube 100 of Fig. 4. This tube is identical with that of Fig. 1 except that it is alsf provided with vertical deflection plates 301a and 30 b.

The horizontal deflection plates 102a, trigger circuit 111, amplifier 106 and photocell 105 are connected in the same manner as before. However interposed between mask 200 and photocell 105 is a red filter 300. As a 4 result, any horizontal motions of the beam about any stable position are corrected by a feedback voltage as before; the red filter prevents the photocell from being rendered responsive to any vertical motions of the beam.

Vertical deflection plate 302a is connected to trigger circuit 311, amplifier 306 and photocell 305 in like manner to the horizontal plate connection. Interposed between mask 200 and photocell 305 is a blue filter 301. As a result, any vertical motions of the beam about any stable position are corrected by a feedbag voltage'from amplifier 306 in the manner previously described; the blue filter prevents photocell 305 from being rendered responsive to any horizontal motions of the beam.

Trigger circuit as before is activated when the beam reaches an extreme horizontal position, i.e. has scanned an array. The amplified shift pulse returns the beam to the other extreme position. Simultaneously trigger circuit 315 is activated to produce a pulse which, after amplification, shifts the beam to a position where it can scan the adjacent array.

Output terminal 112 yields an output voltage which is proportioned to the horizontal beam position in any array.

Such a voltage can be considered a units output volt age. Output terminal 312 yields an output voltage which is proportioned to the vertical position of the beam. Such a voltage can be considered a tens output voltage.

Thus the apparatus of Fig. 4 can also be used as a counter. Moreover, by connecting terminal 312 to a second like counter it is possible to use these counters in cascade and thus indefinitely increase the counting capacity of the system.

The circuit elements shown in block form in Figs. 1 and 4 are conventional in type and are not shown in schematic detail. The photocells and amplifiers, for example, can be of the type shown in item I, Fig. 236II, on page 314, of The Electronic Engineering Handbook, published in 1944 by Electronic Development Associates. The trigger circuits, for example, can be of the type shown in Fig. 6.6 on page 324 of Cathode Ray Tube Displays, published in 1948 by McGraw Hill While I have shown and pointed out and described my invention in one preferred embodiment, it will be apparent to those skilled in the art that many other modifications can be made within the scope and sphere of my invention as defined in the claims which follow.

What is claimed is:

1. In combination with a cathode ray tube provided with means for generating an electron beam, deflection means for deflecting said beam along a given path and a luminescent screen responsive to the deflected beam, a relatively long and narrow optical mask mounted adjacent said screen, the long axis of said mask being coincident with the path of beam deflection, said mask being divided into a plurality of like sections, each section extending the full width of the mask and having a variable transparency characteristic in the direction of beam deflection; means coupled to said deflection means to discretely deflect said beam along said path in such positions that a corresponding point in each section is illuminated in turn; means optically responsive to each illuminated point to derive therefrom a characteristic control voltage; and means to supply said control voltage to said deflection means in a direction opposing changes in beam position within any section when the corresponding point within this any section is illuminated.

2. The combination is set forth in claim 1 wherein the beam is deflected between two extreme positions, and further including beam restoring means responsive to said control voltage and coupled to said deflection means to return the beam to one extreme deflection position when said beam attains the other extreme position.

3. A device for counting a plurality of discretely spaced incoming pulses, said device comprising a cathode ray tube provided with an electron gun for producing an electron beam, deflection plates for deflecting said beam along a given path between two extreme positions, and a luminescent Screen for visually displaying the deflected beam; an optical mask mounted adjacent said screen and provided with a like plurality of identical sections, said mask being so positioned that each section is illuminated in turn as said beam is deflected along said path, each section having a variable light transmission characteristic in the direction of beam deflection; means to supply said pulses to said deflection plates to discretely place said beam in such positions that a corresponding point in each mask section is illuminated in turn, each incoming pulse causing the beam to be deflected from the corresponding point for one section to the corresponding point of the adjacent section, photoelectric means responsive to each of said illuminated points to derive a control 15 2s91842 voltage therefrom; and means to supply said control voltage to said deflection plates in a direction opposing changes in beam position in the absence of any incoming pulse whereby at any instant said control voltage is proportional to the beam position and hence identifies the pulse count.

4. The device as set forth in claim 3 further including means responsive to said control voltage and coupled to said deflection plates to return said beam to one extreme 10 position when the beam attains the other extreme position.

References Cited in the file of this patent UNITED STATES PATENTS Llewellyn Apr. 8, 1952 

